cmd/link: do not read .bss sections in ldpe

For .bss section symbol ldelf does not set P (raw symbol data).
Make ldpe do the same.

Change-Id: Ib3d558456f505ee568d0972465fa9b08b5794a87
Reviewed-on: https://go-review.googlesource.com/42631Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/link/internal/ld/ldpe.go

@@ -162,12 +162,6 @@ func ldpeError(ctxt *Link, input *bio.Reader, pkg string, length int64, pn strin
 			continue
 		}
 
-		data, err := sect.Data()
-		if err != nil {
-			return err
-		}
-		sectdata[sect] = data
-
 		name := fmt.Sprintf("%s(%s)", pkg, sect.Name)
 		s := ctxt.Syms.Lookup(name, localSymVersion)
 
@@ -177,18 +171,6 @@ func ldpeError(ctxt *Link, input *bio.Reader, pkg string, length int64, pn strin
 
 		case IMAGE_SCN_CNT_UNINITIALIZED_DATA | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE: //.bss
 			s.Type = SNOPTRBSS
-			// It seems like this shouldn't happen, but it does, with symbol "runtime/cgo(.bss)".
-			// TODO: Figure out why and either document why it is ok or fix it at the source--
-			// either by eliminating the all-zero data or
-			// by making this SNOPTRDATA (IMAGE_SCN_CNT_INITIALIZED_DATA) to begin with.
-			if len(data) > 0 {
-				for _, x := range data {
-					if x != 0 {
-						Errorf(s, "non-zero data in .bss section: %q", data)
-					}
-				}
-				s.Type = SNOPTRDATA
-			}
 
 		case IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE: //.data
 			s.Type = SNOPTRDATA
@@ -200,8 +182,15 @@ func ldpeError(ctxt *Link, input *bio.Reader, pkg string, length int64, pn strin
 			return fmt.Errorf("unexpected flags %#06x for PE section %s", sect.Characteristics, sect.Name)
 		}
 
+		if s.Type != SNOPTRBSS {
+			data, err := sect.Data()
+			if err != nil {
+				return err
+			}
+			sectdata[sect] = data
 			s.P = data
-		s.Size = int64(len(data))
+		}
+		s.Size = int64(sect.Size)
 		sectsyms[sect] = s
 		if sect.Name == ".rsrc" {
 			setpersrc(ctxt, s)